1. Field of the Invention
The present invention relates to liquid ejection heads used for, e.g., inkjet printers, and nozzle caps and head cap units in the liquid ejection heads, and more particularly, to a liquid ejection head including a reusable nozzle cap and head cap unit that prevents liquid from leaking through nozzles during transport and prevents a nozzle sheet including the nozzles from being damaged when the liquid ejection head is in use and to the nozzle cap and the head cap unit in the liquid ejection head.
2. Description of the Related Art
Liquid ejection heads or printer heads for inkjet printers that are integrated with ink cartridges are known (See Japanese Unexamined Patent Application Publication No. 2003-170606). With this type of printer head, a protective sheet is affixed to a nozzle sheet including nozzles to prevent ink from leaking through the nozzles during transport or storage. When the printer head is used, the protective sheet is removed to expose the nozzles, and the printer head is mounted in the inkjet printer.
Furthermore, printer heads having protective caps for preventing ink leakage are known (See Japanese Unexamined Patent Application Publication Nos. Hei 8-187870 and Hei 8-258276). This type of printer head is provided with a protective cap including a cap body, a sponge, and a protective seal. The sponge presses the protective seal against a nozzle sheet, thereby preventing ink leakage.
However, with the technique disclosed in Japanese Unexamined Patent Application Publication No. 2003-170606, when the protective sheet is removed from the nozzle sheet, the nozzle sheet is stuck to the protective sheet due to the adhesion thereof and is raised in the longitudinal direction. This may damage the surface of the nozzle sheet from which ink is ejected (ejection surface). When the protective sheet has high adhesion, the ejection surface of the nozzle sheet may be broken. Moreover, the protective sheet is still adhesive even after being peeled off. Therefore, when the peeled protective sheet comes into contact with a finger or clothing of a user, ink on the protective sheet adheres to the finger or clothing. On the other hand, if the protective sheet has low adhesion, ink will leak. Therefore, the adhesion of the protective sheet cannot be reduced.
The techniques disclosed in Japanese Unexamined Patent Application Publication Nos. Hei 8-187870 and Hei 8-258276 are effective when the ejection surface of the nozzle sheet is flat. However, when the nozzle sheet has an irregular ejection surface, the hermeticity between the protective seal and the ejection surface is reduced since the protective seal is pressed by a sponge. This causes ink to leak. Once ink leaks due to vibration or the like, the sponge absorbs ink by its capillary action to contaminate the entire protective seal with ink. After the contamination, the protective cap cannot be used again.
The techniques disclosed in Japanese Unexamined Patent Application Publication Nos. 2003-170606 and Hei 8-258276 suffer from a problem when a line head larger than A4 size paper with a wide nozzle sheet is used. More specifically, due to the nozzle sheet being thin, when the size of a nozzle sheet is relatively small, the influence of the adhesion of the protective sheet is negligible. However, when the nozzle sheet has a large area, i.e., larger than A4 size paper, the nozzle sheet is affected by the adhesion of the protective sheet. Moreover, when the nozzle sheet has a large area, it is difficult to uniformly press the protective seal against the entire ejection surface by the sponge. On the other hand, if the stressing force of the sponge is increased, the protective seal might unintentionally adhere to the entire ejection surface.